1. Field of the Invention
The present invention relates to an exposure system for manufacturing semiconductor devices and photolithographic method using the same, and more particularly, to an exposure system for controlling vertical and horizontal critical dimension (CD) difference and a photolithographic method using the same.
2. Description of the Related Art
Generally, each semiconductor devices such as dynamic random access memories (DRAM) includes plural micro-patterns. Such micro-patterns are formed by a photolithography. In order to form the micro-patterns using the photolithography, firstly, a resist layer is coated on an objected layer to be patterned. Next, by performing the photolithographic process, the solubility in regions of the resist layer is changed. Further, the development process is carried out to remove regions whose solubility is changed or not such that resist layer patterns for exposing a part of the objective layer are formed. After this, the exposed part of the objective layer is removed by the photolithography in which the resist layer patterns serves to as etching mask and the resist layer patterns are stripped so that the objective layer patterns are formed.
FIG. 1 is a view illustrating an example of conventional exposure systems.
As shown in FIG. 1, the conventional exposure system 100 includes a light source 110, a reflecting mirror 120, and a condense lens 130. The light source 110 emits a light beam of a predetermined wavelength and includes an illuminating system (not shown) although not depicted in the drawings. The reflecting mirror 120 reflects the light beam emitted from the light source 110 and changes the light path toward the condense lens 130. The condense lens 130 concentrates the light beam reflected by the reflecting mirror 120 and sends the concentrated light beam to a recticle 200 such that the concentrated light beam passes through the recticle 200 and is projected onto a wafer 300.
However, during the photolithography, generally, the critical dimension difference (CD) between the vertical patterns and horizontal patterns may be generated due to various factors. Such factors causing the above-described phenomena are the mask manufacturing process, the photolithography equipment itself, and so on. The phenomena are more baldy generated in an asymmetric illumination system that has been frequently used as of late. Generally, there is an isotropic illumination system such as an annular illumination system, a quad illumination system, a crosspole illumination system, and the like having isotropic properties, and an anitotropic illumination system such as a dipole illumination system having anisotropic properties.
In the conventional exposure system, in order to solve the problem caused by the critical dimension between the vertical patterns and the horizontal patterns, simulations or actual test exposures are carried out several times, and using the result of the simulations or the actual test exposures, the mask is manufactured. However, according to the conventional method, manufacturing the mask again increases manufacturing costs, and it takes much time for testing and certifying the mask whenever the mask is manufactured anew, thereby, becoming a major factor for increasing price of the products.